Top Democrats have privately told GOP leaders that they want David Weprin defeated in tomorrow’s special congressional election for the Anthony Weiner seat in order to send “a wake-up call to President Obama,” a national Republican strategist contends.

Strategist John McLaughlin, a key figure in businessman Bob Turner’s hotly fought and closely watched battle with Queens Assemblyman Weprin, said he’s been startled at how many prominent Democrats say they want the Republicans to win the contest in the heavily Democratic Queens-Brooklyn district to put pressure on the White House.

“It’s really something. We have a lot of Democrats coming to us saying, ‘We hope Turner wins because if Obama doesn’t change his policies, we’re afraid we’re going to lose in 2012,’ ’’ McLaughlin told The Post.

“They’re supporting us as a way to send a wake-up call to President Obama and their party so that there are huge implications nationally from this election,’’ McLaughlin continued.

Former Mayor Ed Koch and Assemblyman Dov Hikind of Brooklyn, both Democrats, have publicly backed Republican Turner because of unhappiness with Obama’s policies toward Israel.

But many other Democrats have far broader concerns as they privately express the fear that the Obama administration’s record of high unemployment, nonexistent job growth and an uncertain business climate could lead to massive GOP victories in next year’s national and state elections.

Nervous city Democrats, meanwhile, have already begun pointing fingers at Rep. Joseph Crowley, the Queens Democratic chairman, as the one most responsible should Weprin, son of former Assembly Speaker Saul Weprin, lose.

“Crowley wanted a candidate who wouldn’t threaten to run against any of the other neighboring Congress members if, as everyone expects, the seat is abolished next year in congressional redistricting,’’ said a prominent Democratic activist.

“And he wanted to do something nice for the Weprin family, so he came up with a terrible, terrible candidate, and we may pay the price on Tuesday,’’ the activist continued.